(1) Field of the Invention
The present invention relates to the transmission of heated fluids. More specifically, the present invention is directed to improved tuyere feed lines for use in the delivery of heated gas to the interior of a furnace. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
(2) Description of the Prior Art
While not limited thereto in its utility, the present invention is particularly well suited for use as an improved tuyere feed line for shaft furnaces. In shaft furnaces, particularly in blast furnaces, preheated air is injected into the furnace through nozzles or tuyeres. The preheated air is delivered to the vicinity of the injection nozzles via a common "hot-blast" main supply, known in the art as a bustle pipe, which is mounted exterior of and around the furnace. A plurality of nozzles, known in the art as blast tuyeres, are located about the periphery of the furnace for discharge into the furnace and these blast tuyeres are connected to the bustle pipe by means of feed lines or conduits known in the art as tuyere stocks.
Prior art tuyere stocks typically comprise a number of tubular members which are lined internally with a refractory material. The individual tuyere stocks are coupled, via flange type connections, to connection sockets provided on the hot gas supply device surrounding the furnace. In order to compensate for mis-alignments, which may arise due to manufacturing and installation inaccuracies, and thermal expansion which occurs during operation, some or all of the tubular members which comprise the individual tuyere stocks are interconnected by means of expansion balls, pivot compensators or similar devices. U.S. Pat. No. 3,662,696 and U.S. application Ser. No. 228,417, now U.S. Pat. No. 3,766,868, both assigned to the same assignee as the present invention, disclose tuyere stock apparatus in which the joints between the individual tubular members are formed by means of universal couplings and cooperating flexible hermetic coupling means. Use of the tuyere stocks of the referenced patent and application will result in the compensation for deformations caused by thermal expansion due to the heated gas in a manner which does not require the use of prior art ball and socket type connecting joints.
In the prior art, including the apparatus of referenced U.S Pat. No. 3,662,696 and copending application Ser. No. 228,417, now U.S. Pat. No. 3,766,868, the injection nozzle portion of the tuyere stock is urged against the blast tuyere in the furnace wall by means of clamping devices in the interest of establishing a leak-proof fluid coupling between these elements. The point of contact between the injection nozzle and the blast tuyere has previously been in the form of a spherical sealing surface defined by the end of the injection nozzle; the use of a spherical joint being in the interest of compensating for any relative angular displacements between these elements. Although the prior art apparatus satisfactorily compensates for most deformations experienced in practice, particularly for thermal expansion and contraction, the injection nozzle of the tuyere stock is often displaced from its central position relative to the blast tuyere cooperating seating surface during operation. Although the spherical sealing surface configuration permits small deviations from the central position, there is an inherent risk that a gap will form at the seating surface between the injection nozzle and blast tuyere. Should such a gap form, the heat transfer relationship between the injection nozzle and the water cooled blast tuyere will be unbalanced and at least a portion of the spherical sealing surface will be subject to a temperature build-up as well as to the impact of the hot air being delivered to the furnace. The temperature rise in combination with the hot air impact will rapidly attack and destroy the spherical seating surface of the tuyere stock. Obviously, the higher the pressure and temperature the faster the erosion of the spherical seating surface will occur. Although the blast tuyere is water cooled, this element is also likely to be damaged and possibly destroyed as a result of the impact of the preheated air against a sealing surface which is at an angle to the direction of gas flow and which is exposed when a gap forms between the blast tuyere and tuyere stock injection nozzle.
Should either the tuyere stock injection nozzle or blast tuyere suffer damage thus requiring the replacement thereof, it is necessary to completely shut-down the furnace. The repair operation is, of course, thus time consuming and expensive. Additionally, the reinsertion of the tuyere stock in a new blast tuyere, or the installation of a new tuyere stock injection nozzle, requires accurate positioning of the elements to insure that a satisfactory seal will be achieved between the injection nozzle and blast tuyere in order to prevent immediate damage to the spherical sealing surface upon resumption of blast furnace operation.